Bradley Cooper had an enormous challenge set before him when he decided to reinvent a Hollywood classic, A Star Is Born, but it turns out casting Lady Gaga in her first leading role was a choice that made the whole project really, really work.

In a new interview with Entertainment Weekly, Cooper stresses that Gaga — who he refers to throughout as Stefani, her given name, as she's billed as Stefani Germanotta on the film's cast list — is directly responsible for the raw performance he delivers in his directorial debut.

"It’s a tribute to her generosity as an artist," he says of A Star Is Born and Gaga as its muse, and specifically in regards to her affect on his portrayal of Jackson. "She made me so comfortable, from day one. When I first met her to talk about the role, I asked her if we could sing this folk song together, because if there’s no chemistry or we can’t sing together, it won’t work, but she just sat down and made me feel comfortable, and from then on it was that way. I had the benefit of preparation. By the time we shot the movie… in some ways I was able to hide in him, so I never had to deal with the reality of asking myself, ‘Are you nuts, putting yourself on stage with Lady Gaga?’ That never really entered into my head, thank God!"

The story follows Cooper as Jackson Maine, a grizzled, jaded musician, and Gaga as Ally, an aspiring singer and his protégé, as the two grapple with the heartbreak and triumphs that pepper the pursuit of the rock 'n' roll dream. Three previous interpretations of the story have seen the major motion picture treatment, with Judy Garland and Barbra Streisand playing leading the 1954 and 1976 versions, respectively.

But did Judy and Babs directly affect the acting of their costars, or the development of their characters, or even write a chunk of the soundtrack? That's a distinction Gaga may hold on her own, as Cooper is adamant that the expertise and perspective she brought the set of A Star Is Born shaped his performance — and the role music was written for the movie on the whole.

"There’s always been a meta element to the tradition of A Star Is Born, in that it has to be somebody like Judy Garland, Barbra Streisand, or Lady Gaga playing the role," he continued. "In that sense, you’ll be blown away by what Stefani’s created."

Cooper divulged quite a bit of information about the music of the movie, which involves compositions from Gaga, collaborations with Mark Ronson (who she last teamed up with on Joanne, and additional writing from Lukas Nelson — Willie's son, and one who'll play a member of Jackson's character's band in the movie — and southern rocker Jason Isbell.

"We’re honored to have incredible writers on the movie, because all the music is original, and it’s all sung and recorded live," he explained. "There’s no singing in playback, which was terrifying, but it’s key to the movie! It makes all the difference. Stefani was adamant about that: she said, ‘We have to record everything live,’ and I’m so glad she did. It’s night and day."

And even when Cooper was writing songs himself, Gaga's advice guided his pen: "For Jackson’s music, [Stefani] gave me the inspiration, she just said, ‘Work, and then you’ll figure out what kind of musician he is,’ and that’s really what happened. I had the luxury of time."